The present invention relates in general to blood drawing systems, and in particular to a blood drawing system which, in one embodiment, permits negative pressure control within a vessel to which blood is drawn for preventing vessel collapse because of excess pressure, and, in a second embodiment, for removing and conserving for re-introduction medicament liquid fed through an intravenous conduit prior to blood withdrawal through the intravenous conduit to a negative-pressure collection vessel.
Employment of negative-pressure vessels for collecting blood samples from arterial or venous blood vessels of living beings is a common practice in medical treatments where subsequent laboratory analysis of the blood samples so collected helps in diagnosing and treating illnesses. In those who are relatively healthy, the use of standard negative-pressure collection vessels, as exemplified by VACUTAINER brand tubes manufactured by Becton Dickinson, provide excellent withdrawal properties without causing vessel collapse. However, in patients whose vascular system is fragile, the negative pressure within a vacuum tube can be excessive, and such excessive negative pressure can cause vessel collapse as suction from the vacuum tube attempts to extract a blood sample.
At the present time, phlebotomists overcome this problem by drawing the blood sample into a standard syringe where negative pressure application can be controlled by the speed at which the plunger of the syringe is withdrawn. In this manner blood can be withdrawn slowly and without vessel collapse. However, the blood so drawn into a syringe then must be transferred to a vacuum tube because of required anticoagulant and/or other blood-preservation additives present in the vacuum tube. Such transfer can only be accomplished by attaching a standard hollow needle to the syringe, piercing the stopper can of the vacuum tube, and expelling the syringe content into the vacuum tube. As is recognized to those with ordinary skill in the art, the above-described attachment of the needle to the syringe is potentially a very dangerous event because an easily-occurring finger-stick of the technician performing the task can mean the transfer of patient blood to the technician along with blood-borne disease. Therefore, a primary object of the present invention is to permit blood transfer from a drawing syringe to a negative-pressure collection vessel through a closed network not requiring attachment of a needle to the syringe.
A second situation where blood-sample withdrawal is required is in connection with a typical intravenous drip line having a port to which a negative-pressure collection vessel (e.g. a vacuum tube) can be connected for easy blood withdrawal through the line. As is evident, however, if the line is not first cleared of drip-liquid, any blood sample will have a high amount of such medicament liquid and therefore will not provide a true blood-only sample. This problem presently is addressed by turning off the drip from its source and thereafter withdrawing and discarding all fluid from the drip line prior to opening the port to the vacuum tube. As is evident, this approach not only decreases (and wastes) the intended drip-liquid amount for the patient, but also causes loss of at least a small amount of blood from the patient as the drip line is filled with only blood for vacuum tube collection. One or both of these disadvantages can be harmful to a patient. In particular, if the amount of drip-liquid to be delivered to a patient is critical, such amount is automatically compromised with drip-liquid loss. Second, if the patient is a neonatal child with a corresponding very low volume of blood, even a small blood loss which occurs during each drip line clearance can create a dangerous health hazard. Consequently, a second object of the present invention is to provide a closed drip-line system in which medicament liquid cleared from the drip line prior to blood withdrawal into the vacuum tube is collected for reintroduction after the blood sample has been drawn. In this manner, both drip-liquid and blood volume are conserved for the patient.
These and other objects of the present invention will become apparent throughout the description thereof which now follows.